Machine for applying joint or edge stripping to wire mesh screen



Jan. '17, 1939. J 2,144,570

MACHINE FOR APPLYING JOINT OR EDGE STRIPPINC' TO WIRE MESH SCREEN Filed Aug. 26, 1937 15 Sheets-Sheet 1 WWW/9 m J 7, I939- A. JEHARRISON 2,144,570

MACHINE FOR APPLYING JOINT OR EDGE STRIPPINC- TO WIRE MESH SCREEN Filed Aug. 26, 1957 15 Sheets-Sheet 2 WWW Jan. 17; 1939; A. J. HARRISON 2,144,570

MACHINE FOR APPLYING JOINT OR EDGE STRIPPINC- TO WIRE MESH SCREEN Filed Au .'26, 1957 15 Sheets-Sheet 3 gap a; JWf/ W Jan. 17, 1939. J HARRISON 2,144,570

MACHINE FOR APPLYING JOINT OR EDGE STRIPPINC- TO WIRE MESH SCREEN Filed Aug. 26, 1957 15 Sheets-Sheet 4 Jan. 17, 1939. A. J. HARRISON 2,144,570

' MACHINE FOR APPLYING JOINT OR EDGE STRIPPING TO WIRE MESH SCREEN Filed Aug. 26, 1937 15 Sheets-Sheet 5 Jan. 17, 1939. A. J. HARRISON ,1

MACHINE; FOR APPLYING JOINT OR EDGE STRIPPING TO WIRE MESH SCREEN Filed Aug. 26, 1957 15 Sheets-Sheet 6 zgggrZ V AM cZHar/"LQYW g @4452?? J Jan. 17, 1939. A. J HARRISON MACHINE FOR APPLYING JOINT OR EDGE STRIPPINC- TO WIRE MESH SCREEN Filed Aug. 26, 1957 15 Sheets-Sheet 7 I I 4 A 1 Il i V 6% Jan. 17, 1939. HARRISON 2,144,570

MACHINE FOR APPLYING JOINT OR EDGE STRIPPINC- TO WIRE MESH SCREEN Filed Aug. 26, 1957 15 SheetsFSheet 8 Jan. 17, 1939. A.IJ. HARRISON 2,144,570

MACHINE FOR APPLYING JOINT OR EDGE STHIPFING IO WIRE MESH SCREEN Filed Aug. 26, 1957 15 Sheets-Sheet 9 Jan. 17, 1939. A; J ARR ON 2,144,570

MACHINE FOR APPLYING JOINT OR EDGE STRIPPINC- TO WIRE ME sH SCREEN Filed Aug, 26, 1957 15 Sheets-Sheet 10 JW+ 445m Ji /735W Jan. 17, 1939. A. Jv HARRISON MACHINE FOR APPLYING JOINT OR EDGE STRIPPINC- TO WIRE MESH SCREEN Filed Aug. 26, 195'? 15 Sheets-Sheet ll may Jan. 17, 1939. A. J. HARRISON 2,144,570

MACHINE FOR APPLYING JOINT OR EDGE STRIPPING T0 WIRE MESH SCREEN Filed Aug. 26, 1957' 15 SheetsSheet 12 1 Jan. 17, 1939. A. J. HARRISON 2,144,570

MACHINE FOR APPLYING JOINT OR EDGE STRIPPING TO WIRE MESH SCREEN Filed Aug. 26, 1937 15 Sheets-Sheet l5 Jan. 17, 1939 A J. HARFiSON 2,144,570

MACHINE FOR APPLYING' JOINT OR EDGE STRIPPING TO WIRE MESH SCREEN Filed Au 26, 1937 15 SheetsSheet 14 IRE MESH SCREEN l5 SheetSSheet l5 Jan. 17, 1939. A. .1. HARRISON MACHINE FOR APPLYING JOINT OR EDGE STRIPPING TO W Filed Aug. 26, 1937 Patented Jan. 17, 1939 UNITED STATES MACHINE FOR APPLYING JOINT OR EDGE STRIPPING TO WIRE MESH SCREEN Alma J. Harrison, Philadelphia, Pa., assignor to Proctor & Schwartz, Incorporated, Philadelphia, Pa., a corporation of Pennsylvania Application August 26, 1937, Serial No. 161,119 39 Claims. (01.153-1) This invention relates to an apparatus for applying hinge strips to opposite edges respec tively of the units of wire mesh screen which collectively form the body of a conveyer apron of a jointed sectional type, such, for example, as that illustrated in U. S. Letters Patent No. 2,007,862, dated July 9, 1935.

In the sectional type of conveyer, especially in cases where the conveyerincludes side chains composed of pivotally connected links, and which in some instances is provided with cross 'girts extending from one side chain of the conveyer to the opposite side chain thereof, and wherein the screening of which the body or apron of the conveyer is composed extends from side to side of the conveyer and is connected to the links of the side chains with longitudinally adjacent I sections of the screen hinged-or pivotally connected together transversely of the conveyer, it is especially important that the axes of the hingejoints connecting the successive screen sections or units be parallel to each other and in accurate axial alignment with the pintles of the linksof the side chains in order that the screen sections of a conveyer apron will pivot accurately and smoothly with the links of the side chains of the conveyer .as the side chains pass around the sprocket wheels by which the conveyer as a whole is driven or guided.

It is also important that the screen units be made and maintained as flat as possible in order to prevent displacement of the material being transported by the conveyer, which is frequently of a loose nature laid in a substantially uniform layer on the screen, as the conveyer moves under load.

One object of the invention is to apply a hingeforming strip to each of a pair of substantially parallel edges of each screen unit in a manner to form a multiplicity of hinge rod bearings along each of said edges, with the axes of the multiplicity of bearings in true axial alignment wtih each other across the full width of the conveyer section or unit, at each side thereof,

, withthe hearings on one side in staggered relation to those on the opposite side of the unit.

Another object of the invention is to space the axes of the hinge rod bearings on the opposite sides of the unit accurately to a predetermined dimension between said axes. I

Other objects of the invention, as will appear more fully hereinafter, are to line up the opposite edges of each unit parallel to each other preparatory to the securing of the hinge strips to the screen sections; to flattenv each unit intermediate the parallel edges thereof; to form the axes of the hinge rod bearings on the opposite sides of the unit parallel to each other and to said aligned edges respectively, in spaced rela:

in said accurate predetermined spaced relation 10 to each other.

The construction and operation of the apparatus forming the subject of the present invention will be fully disclosed hereinafter, reference being had to the accompanying drawings; of which:

Figs. 1a, 1b and 1c collectively constitute a front elevation of the machine;

Figs. 2a., 2b and 2c collectively constitute a plan view of the machine shown in Figs. 1a, 1b and 1c respectively;

Fig. 3 is a fragmentary rear elevation of a portion of the mechanism shown in Figs. 1a and 2a.;

Fig. 4 is a transverse sectional elevation taken on the line 4-4, Fig. 2a.;

Fig. 5 is a transverse sectional elevation take on the line 5-5, Fig. 2b; 7

Fig. 6 is a plan View of the mechanism shown in Fig. 5;

Fig. 7 is a longitudinal sectional elevation taken on the line l1, Fig. 6;

Fig. 8 .is a longitudinal sectional elevation taken on the line 88, Fig. 6;

Fig. 9 is a sectional elevation taken on the line 99, Fig. 8; I

Fig. 10 is a detached perspective view of a portion of the mechanism shown in Figs. 8 and 9;

Fig. 11 is an enlarged transverse sectional elevation taken on the line lll I, Fig. 21), showing the screen flattening and edge-aligning means in cooperating relation to each other, with the hinge strips in place to be secured to the opposite edges of the screen unit;

Figs. 12 and 13 are views similar to Fig. 11 but showing the edge-aligning and strip-holding elements in relatively different positions;

Fig. 14 is a detached perspective view of the pressure or flattening plate used in the apparatus and shown in operative position in Figs. 5 and 11 respectively;

Fig. 15 is a detached perspective view of the centering means for the pressure plate of Fig. 14;

Fig. 16 is an enlarged front elevation, partly in section, of a portion of the mechanism for controlling the pressure plate of Fig. 14;

Fig. 17 is a detached perspective view, partly in section, of the mechanism for actuating the pressure plate controlling means of Fig. 16;

Fig. 18 is a perspective view of a flexible removable mandrel wire around which the hinge rod bearings are formed and which also holds the hinge strips in place for and during the bearing-forming operation;

Fig. 19 is a detached perspective view of a I passed through the spaced openings in the wire mesh screening preparatory to bending and clinching by the shoe shown in Fig. 19;

Fig. 23 is a sectional elevation illustrating the initial set of prongs of the strip of Fig. 22 being acted upon'by the clinching shoe of Figs. 19 and 20; 7 r

Fig. 24 is a view similar to Fig. 23 showing the second set of prongs of the hinge strip being acted upon by an initial bending wheel similar to that shown in Fig. 21; g

Fig. 25 is a perspective view similar to Fig. 22

showing the screen and strip after having been acted upon by the shoe and wheel of Figs. 23 and 24 respectively;

Fig. 26 is a view similar. to Fig. 24 but showing the secondary bending wheel acting upon the secondary prongs of the hinge strip;

Fig. 2'7 is a view similar to Figs. 22 and 25 and showing the screen and strip after being acted upon by the second bending wheel of Fig. 26;

Fig. 28 is a view similar to Fig. 26 but illustrating the screen and strip being acted upon by a final prong setting wheel to complete the hinge rod bearings and to anchor the strip permanently to the screen; 1

Fig. 29 shows the screen and strip of Figs. 22, 25 and 27 after engagement by the final setting wheel of Fig. 28;

Figs. 30 and 31 are fragmentary views of the opposite faces of fragmentary portions of two sections or units of screen joinedby a hinge rod passing through the staggered intermeshing bearings of the two units respectively secured ends of a long strip of screening joined to form a continuous. belt;

Fig. 32 is a transverse section through one longitudinal edge of a screen unit orcontinuous strip showing the hinge strip employed as a selvage or edge reinforcement;

Fig. 33 is a perspective View of the edging or hinge-forming strip in blank form prior to im. tial longitudinalbending for subsequent introduction into the machine; and v Fig. 34 is a perspective view of a modified form of strip blank.

The construction of a wire mesh screen commonly used in conveyer aprons is clearly shown 7 fabric from that on which 7 wardly from the opposite side of the body strip 2 in staggered relation to the short prongs 2 projectsa series of relatively long prongs 2 V The strip 2 after being formed in the fiat blank illustrated in Fig. 33 is bent transversely on a line substantially midway between the points a and 2 of the prongs 2 and 2 respectively, leaving the body strip a and prongs a lying in one plane and the long prongs. 2 throughout a substantial portion of their length lying in a plane approximately at 60 to the plane of the main body strip 2 and prongs 2 The pointed tips s and 2 of the prong e and 2 respectively are respectivelybent at an angle of about 60 to the planes of'the major portions of the prongs, with a gap 2 between the points. as clearly shown in'Figs. 11, 22 and'23.

The opposite longitudinal edges y and 21 "of the'screen at are initially inserted in the gaps superposed'relation to the small prongs a and the body strip 2 with the edges .11 and g substanially in alignment with those edges 2 of the body strip e from which the long prongs 2 pmject and with the tips 2 of the short prongs e projecting upwardly throughl alternate spaces :6 of the screen :17, as clearly shown in Fig. 22.

The tips 2 of. the short prongs a are then bent and clinched tightly around a longitudinal wire .13 of the screenqm lying between the prong tips and the'adjacen't outer edge of the screen unit :0, as clearly shown in Fig;25'.

The longprongs '2 are then bentrdownwardly around a removable mandrel in the form" of a flexible wire 10, until the tips 2 of said long prongs 2 enter the openings 20 of the screen a: which lie intermediate and in the next row removed fromthose through which the prong tips 2 of the short prongs 2 project. 7

'The tips. 2 0f the long prong e are then clinched on theopposite face of the wire mesh the points or tips a of the short prongs 2 are clinch shown in Figs. 28 and 29.

The bending of the long prongs e aroundthe mandrel wire 20 forms the long prongs .2 into a series of axially aligned pivot rod strap bearings a, a which alternate with recesses b, b therebetween along each of the opposite sides'or edges 1/ and 1/ ofthe screen unit at, with the axes of' the rod-receiving openings 0 of said strap bearings a in axial alignment with each other and in spaced relation to the opposite edges y and 1/ of the screen unit 3:; and with the bearing straps a on the one edge 1 of the unit x disposed opposite the recesses I) along the opposite edge y" of the unit :11; and with the axis 0 of the edge strip a lying along'the edge. 11 of the unit x in parallel relation to the axis 0 of the edge or hinge strip 2 disposed along the opposite edge, y of the unit :13, whereby the units a:- a: may be connected together by hinjge rods d for pivotal movement with respect to each other about the d, as clearly li n xe a c d e oi cid n ax s f the rod d.

The opposite transversely extending ends :0 of connected adjacent units as, a: are substantially in alignment with each other, due to the staggering of the bearing straps a, or along the opposite longitudinal edges y and y? of each unit at, for attachment to the links of the side chains of the conveyer whensuch side chains are employed. I

The-transverse edges x of the screen sections or units of the sectional conveyer-are normally secured to the links of the side chains of the conveyer in the manner illustrated in the above noted U. S. patent and in U. S. Patent No. 1,634,963, dated July 5, 1927, with the axes of the hinge rods d in axial alignment with the. chain pintles by which the links of the chains are pivotally connected to each other. 7 r

The hinge rods d as shown in Figs. 30 and 31 pass through the staggered bearing straps a, of the two adjoining sections as, a: of the conveyer, to provide for pivotal movement of the one section with respect to the other when the links of the side chains of-the conveyer pivot with respect to each other'in passing around sprocket wheels which drive or guide the conveyer.

The apparatus for applying the edge or hinge strips 2 to the screen sections :1: comprises aframework l of any suitable construction. Mounted on the framework in fixed relation thereto, is a table or bed 2 provided with an upper horizontally disposed surface 3 for receiving a section or unit of screen .12.

At each of its opposite sides, and extending longitudinally of the table 2, are gauge bars 4 and 5 respectively. The gauge bars 4 and 5 are provided with inner vertical edges 6 and l which are adapted to engage the opposite longitudinal edges y and 1 respectively of the screen unit :n therebetween. The gauge edges 6 and l are spaced apart to a predetermined distance during the application of the edge or hinge strips 2, z thereto. This controls the ultimate width of the unit an between its opposite longitudinal edges 3/ and y r Spaced inwardly from the screen-engaging edges 6 and I of the gauge bars 4 and 5 and at a predetermined distance from said gauge edges, the gauge bars are bored longitudinally, substantially in the same plane as the unit 1:, as indicated at 8 and 9, for reception of the mandrel wires w. a

The upper portions of the gauge edges 6 and 1 flare outwardly, as indicated at W and H. The gauge edges of the gauge bars 4 and 5 are provided with a series of undercut grooves or recesses l2 and I3 respectively which are spaced apart along said gauge edges a distance substantially equal to the spacing of the long'prongs 2 of the edge strips 2, for receiving those portions of the initially bentlong prongs which eventually form the bearing straps a, a, in the manner shown in Fig. 13, and providing projections M and I5 between the recesses l2, l2 and l3, l3 respectively which extend into the spaces 1) provided between the long prongs 2 2. and the ultimate strap bearings a, a.

In addition to engaging the opposite edges 11 and 1/ of each screen unit at, the forward edges 6 and 1 of the projections l4 and I5 engage the edges z" of the body strip 2 of the strips 2 and 1 position the initially bent strips 2 in definite predetermined relation to each other and to the edges 1/1 and 1/2 of the screen unit a: transversely across the table surface 3, with the initial longibores 8 and 9 of the gaugebars 4 and 5 respectively, whereupon the mandrel wires 10 are threaded through the bores 8 and 9 and through the bends of the strips 2:, 2, whereby said strips 2, z are secured in definite positions on the table 2 for receiving the Wire screen as within the gaps .2 of the edge or hinge strips 2, z.

The screen-receiving surface 3 of the table 2 is provided with relatively shallow grooves along and parallel to its opposite longitudinal edges. The depth of the grooves below the screen-receiving surface 3 is substantially equal to the thickness of the metal of which the strips 2, z is composed.

The gauge bar 4 is held in a fixed position insofar as lateral movement is concerned but said bar is carried by a bar l8 which is arranged for vertical movement in a guide groove l9 formed in an overhanging portion 20 of and located at one side of the table 2.

The gauge bar 5 receives lateral as well as vertical movement and is secured to a bar 2| which is movable vertically and horizontally with respect to the screen-supporting surface 3 of the table 2.

' The carrier bar 2| of the gauge bar 5 is provided at spaced intervals along its length with a plurality of laterally extending arms 22. The

arms 22, 22 are mounted in recesses 23, 23 respectively which are formed in the body portion of the table 2. The inner ends of the arms 22 are provided with upper and lower arcuate surfaces.

24 and 25 respectively which are formed on arcs swung from a common center 26. These concentric arcs function as a fulcrum for said drums from the relatively fixed gauge bar 4, is effected by means of springs 21 which are mountedin counterbores 28 formed in the table 2, one end of each spring bearing against the base of the counterbore with the opposite end of the spring bearing against the inner end of the arm 22.

Movement of the carrier bar 2| and gauge bar 5 inwardly, that is, toward the relatively fixed gauge bar 4, is accomplishedby means of a heavy shaft 29 which is pivotally mounted on the table 2, beneath the said table, by means of bearing brackets 38. The shaft 29 is provided with lugs or arms 3| which project vertically through slots or, recesses 32 formed in thetable 2 and recesses 33 formed in the arms 22 of the carrier bar 2|.

Vertical movement of the carrier bars I8 and 2|, to which the gauge bars 2 and 5 are respectively secured is accomplished by means of a pair of cam bars as and 35 which extend longitudinally of the table 2 and are slidably mounted in guideways 36 and 37 formed in the table 2. The cam bars 32 and 35 are provided on their upper sides with cam surfaces 38 and 39. The cam surfaces 35 and 39 engage the lower ends of plungers 4i! and 4| respectively which are verticaly slidably mounted in bearing openings 42 and 43 formed in the table 2, beneath the carrier bars l8 and 2| respectively.

Rocking motion of the shaft 28, to move the gauge bar 5 toward and away from the gauge.

The upper ends of the arms 44 and 45 are provided with bosses '46, 46 which receive reduced ends 41,41 of a spacing bar 48. Pivotally mounted on the spacing bar 48 is a sleeve 49 from which project handles or levers 50, 58 arranged at spaced intervals along the sleeve 49. V V

The sleeve 49 is provided with a pair of relatively spaced horizontally disposed levers 5!, 5| which extend rearwardly from the sleeve 49. The levers 5|, 5| are provided at their rear ends with lugs or pins 52 which normally rest on horizontal surfaces 53 formed on brackets 54 which are adjustably mounted" on the frame I by.

means of screws 55, as shown in Fig. 4;

The guage' bar 5 is held in its innermost posi- 7 tion, that is, its position nearest to the guage bar 7 4, against the action of the springs?! which tend to move said guage bar 5 in the opposite direction, by, the lugs or pins 52 on the arms 5| engaging shoulders 56 formed on the brackets 54.

To move the gauge bar 5 outwardly, i. e. in a direction away from the guage bar 4, thehandles 58 are operated to rock the sleeve 49 and consequently the levers 5! until the lugs or pins 52 rise abovethe upper edges of the shoulders 56, where' 7 upon said springs 21 assisted by manually pulling on the handles 50 rocks theshaft 29 and causes said lugs or pins 52 to ride along a horizontal surface 51 which is formed on the bracket 54 in elevated relation to the horizontal surfaces 53 thereon.

Upward movement of the levers 5| is limited by the upper ends 58 of stop levers 59 which project laterally over the levers 5! and function ,as stops for said levers. The levers 59 are pivotally connected'at 59a to the brackets 54.

Outward movement of the guage bar 5 is limited by the lugs or pins 52 engaging sides 5% of the stop levers 59, the opposite sides 590 of said stop levers being engaged by adjustable abutments in the form of screws 59d carried by the brackets 54.

Inward movement of the gauge-bar 5 toward the gauge bar 4 is resisted by the screen section itself which, as previously noted, hasone edge in engagement with the gauge edge 6 of the relatively fixed gauge bar 4 and the opposite edge 3/ in engagement with the gauge surface 1 of the relatively movable gauge bar 5, when the movement of, the bar 5 toward the bar 4 tends to compress the screen an transversely. Lateral compression of the screen'rcontinues until the lugs or pins 52 drop behind the shoulders 56 and hold the gauge bar 5 in definite spaced relation to the gauge bar 4 with the screen unit a: under compression between the two on the surface 3 of the table 2.

Vertical movement of the gauge bars 4 and 5 with respect to the screen-supporting surface 3,

as provided for by the longitudinal movement of the cam bars 34 and 35, is efiected by the cam bars 34 and'35 being provided adjacent one end of each of said bars with a gear rack'Bll, the teeth of which intermeshwith the teeth of pinions 6| which are secured to a shaft 62 which is rotatably mounted in the frame of the machine. The shaft 62 is provided with a lever 63 by which said shaft and gears 6| may be rotated or oscillated to provide longitudinal reciprocation of the cam bars 34 and in unison.

' Connected at 64 to the lever53 is one endof a link 65, the opposite end of which" is pivotally connected at 66 to an actuating bar 61. The

' actuating bar 6'! extends along the front of the ating bar 61 and extend vertically therefrom.

The rear ends of the levers 18 are pivoted at 13 to stationary portions of the frame I.

By swinging one or the other or both of the levers 18 to the left, from the position shown in Figs.- 1b and 1c, the actuating bar 6! is correspondingly moved to the left which, through the link 65 and lever'63, rocks the shaft 62 and gears 6 I in a clockwise direction andtransmits a reverse movement to the cam bars 34 and 35 which,

through the cam surfaces 38 and 39 thereon, move the plungers '48and 4| vertically in the table 2 with a consequentraising of the carrier bars 18 and 2| and the gauge bars 4 and 5 respectively carried thereby. V

The vertical unisonal movement of the gauge bars 4 and 5 and the relative outward movement of' the gauge bar 5 with respect to the gauge bar 4 is effected only at the time of releasing the screen section :r' from theapparatus after the edge strips 2, 2 have been appliedthereto and after'the mandrel wires whavebeen withdrawn from the bores 8 and 9 of the gauge bars 4 and 5 and out of the hinge rod bearings a which have been formed around said mandrels.

The lateral compressive" force under which the screen unit or section a: is placed, by movement of the gauge bar 5 towardthe gauge bar 4' after the screen unit has been placed on the receiving surface 3 of the table 2, if the opposite edges 1/ and 1/ of the screen section have not been accurately cut tends to cause the screen section or unit a: to'buckle upwardly from the surface 3 of the tabler2 between the gauge bars 4 and 5. Such buckling is prevented or corrected by means of a pressure plate 15, shown particularly in'Figs.

4, 5, 10 and 14.

The pressure plate. 15 is adapted to be removed from the table 2 to lie behind said table in substantially parallel relation thereto, as indicated in Fig. 4, and for that reason said plate is adapted to be attached and detached to and from a carriage 80 which is movable horizontally toward and from the table 2.

The pressure plate 15 is adaptedto be supported in its inoperative position clear of the table 2 by means of a pair of hooks 16, "I6, shownrin Figs. 1b andlfi. The hooks 76, 16 are provided at their lower ends respectively with opposed inclined surfaces 16a; 16a. The lower ends of the hook members"; are each arranged to enter a recess 11 formed in the upper surfaceof the pressure plate 15. One end of each of the recesses is provided with an undercutinclined surface Tia,

angles with respect to each other and the undercut surfaces 11a, 11a of the recesses 11, 11 respectivelyof the pressure plate 15 are corresspondingly disposed at angles opposite to each other.

The hook members 16, 16 are pivotally mounted for movementin opposite directions about pivots 18, 18 which are carried by a front bar 19 of a rocking frame 8| which form part of the pressure plate carriage 80. The frame 8| of the carriage 80 also includes arms 82, 82 which are secured to and project rearwardly from the bar 19 and are pivotally mounted at'their rear ends on a shaft 83 supported by the carriage 80. The opposite ends of the shaft 83 are secured in bars 84 forming part of the carriage 80 and which are mounted for horizontal reciprocation in the direction transversely to the table 2 between supporting and guide rollers 85, 85. The rollers 85 are rotatably supported in suitable bearings carried by the main frame of the machine.

Rocking of the hook members 16, 19 about their respective pivots 18, 18 simultaneously, in opposite directions, to release or to pick up the pressure plate 15, is effected by means of a pair of controlling bars 86, 86. The control bars 86, 86 are slidablymounted in bearings 81, 81 and 88, 88 carried by the front member 19 of the carriage 80. The control bars86 are provided with laterally extending pins 86a, 880. which project into slots 181) formed in the upper ends of the hook members 16. 7

Movement of the control bars 86, 86 toward each other, to release the hooks 16, 16 from the pressure plate 15," is effected by compression springs 89, 89 confined between the extreme outer ends of the control bars 88, 86 respectively and the bearings 88, 88 in which said extreme outer ends of said control bars are slidably mounted.

The inner ends of the control bars 86, 86, which are slidably mounted in the bearings 81, 81, are provided with rollers 90 which bear against cam surfaces formed on the opposite edges 9|, 9| respectively of a vertically reciprocable actuating bar 92. The actuating bar 92 is slidably mounted in a framework 93 carried by the front bar 19 of the carriage 80.- One edge of the actuating bar 92 is provided with gear teeth 94 which'intermesh with the teeth of a pinion 95. The pinion 95 is secured to a shaft 96 which is rotatably mounted in the framework 93. Also secured to the shaft 96 is a hub 91 of a crank handle 98. Turning of the crank 98 raises and lowers the actuating bar 92 and moves the cam surfaces formed on the opposite edges 9| thereof relative to the rollers 90 carried by the opposed inner ends of the axially aligned control bars 86, 86.

When the bars 86, 86 are moved in opposite directions by the cams 9|, 9| the hook members 18 are actuated to pick up the pressure plate 15 and when said bars are moved in the opposite directions by the springs 89, said hooks release the pressure plate 15.

The outer end of the crank lever 98 is connected at 99 to an operating bar I which extends longitudinally of the machine and is connected at its opposite ends to crank levers 98a and 980 which are pivotally mounted at 96a and 960 respectively, to brackets 93a and 930 respectively, I

as shown in Figs. 1a. and 10, respectively, said brackets 93a and 930, like the bracket 93, being secured to the front bar 19 of the pressure plate carriage 80.

Movement of the pressure plate 15 from its inoperative position behind the table 2, as shown in Fig.4, to its operative position on the table 2, as shown in Fig. 11, is efiected manually, through a horizontally extending handle bar IOI.

The handle bar IOI is secured at its opposite ends in the end members 82, 82 respectively of the pressure plate lifting frame 8|. Within the openings I04 the shaft I03 is provided with ovalshaped cams I06, which, with the handle bar |0| in the full line position of Fig. 4, maintains the pressure plate frame 8| and the pressure plate 15 in an elevated position with respect to the slide bars 84 and to the screen-supporting surface 3 of the table 2. The levers I02, |02bear against edges I01 of the carriage member 19, whereby the whole of the pressure plate supporting mechanism supported by the carriage 80 including the slide bars 84 and the frame 8| pivoted to said slide bars may be moved from the .inoperative position shown in full linesin Fig. 4 to a position tion to the screen-supporting surface 3 of the table 2, as shown in broken lines in Fig. 4, such movement being effected by pulling the handle bar IOI outwardly, toward the table 2, which causes the slide bars 84 to move through the supporting rollers 85 until the broken line position of the pressure plate is attained.

The pressure plate 15 is lowered from the broken line position of Fig. 4 to the full line position of Fig. 11 by moving the handle bar I 0| rearwardly, from the full line position, Fig. 4, to the broken line position, Fig. 4, which causes the wherein the pressure plate 15 is in overlying relashaft I03 to rotate in the slide bars 84 with a corresponding rotation of the cams I 06, which causes the frame 8| to swing about the pivot shaft 83. This lowers the pressure plate 15 to a position resting upon the screen a: which has been previously laid on the table 2.

With the pressure plate 15 in its low or screenengaging position, the hooks 16 are operated from the full line positions in Fig. 16 to the broken line position in said figure, which releases the pressure plate 15, leaving the full weight thereof resting on the screen a:. l

Normally the dead weight of the pressure plate 15 flattens the screen 1: between the lower face of the plate 15 and the screen-supporting surface 3 of the table 2, from the gauge bar 4 to the gauge bar 5, causing the wires of which the screen is composed to readjust themselves under the weight of the pressure'plate 15 whereby any bulging or warping of the screen unit, as causedby the aligning of the opposite edges y and y by the gauge bars 4 and 5-in the manner above noted is corrected. This causes the screen a: to assume a perfectly fiat condition in a single plane.

After releasing the pressure plate 15, in the manner noted, its supporting carriage 80 is returned to the inoperative position of Fig. 4 with the levers I02 remaining in the broken line position in said figure.

The pressure plate 15 is centered with respect to the gauge bars 4 and 5 by means of guide blocks I08 which are secured to the screen-supporting surface 3 of the table 2 adjacent the opposite ends respectively of the gauge bars 4 and 5, beyond the opposite transverse ends of the screen unit 0:, said blocks being recessed at I09, as shown in Figs. 2a, 2a and 15, for the reception of longitudinally projecting lugs or extensions 

